Several antigonadotropic substances have been isolated from extracts of pineal glands including certain indoles, vasotocin and other substances of unknown character. Yet the question of the nature of the antigonadotropin responsible for apparent pineal function has not been answered, although the potential significance of such a hormone is recognized and is currently under wide consideration. The applicant has partially purified a substance from aqueous extracts of bovine and ovine pineal glands that is more active than the indole melatonin, a suggested pineal hormone. The pineal antigonadotropin is postulated to be a small polypeptide. When injected into mice and rats this potential hormone retards puberty, reduces the weight of the gonads and accessory reproductive organs, inhibits fertility and blocks ovulation. In studies employing radioimmunoassays for gonadotropins, the pineal antigonadotropin has been observed to inhibit the postcastration rise in serum luteinizing hormone in male rats. We propose to continue work on the characterization of ovine pineal antigonadotropin using isolation methods established in our laboratory. These include gel filtration, ultrafiltration, partition chromatography, ion exchange chromatography, thin layer chromatography, electrophoresis and quantitative amino acid analysis. A determination of the sequence (structure) of the compound will be undertaken and synthesis of the compound will be carried out in order that comparisons with the natural product can be made. Studies on the effects of the purified antigonadotropin on the development of puberty in immature animals, and others relating to the inhibition of ovulation in adult female rats, will be continued. A search will be made for the site and mechanism of action of the antigonadotropin.